Electronic converters for light sources comprising, for example, at least one LED (Light Emitting Diode) or other solid state lighting means normally supply a direct current at their outputs. This current can be constant or variable over time, for example in order to regulate the brightness of the light emitted by the light source (by what is known as the “dimming” function).
FIG. 1 shows a possible lighting system comprising an electronic converter 10 and a lighting module 20, comprising, for example, at least one LED L. The electronic converter 10 normally comprises a control circuit 102 and a power circuit 104 (such as an AC/DC or DC/DC switching power supply) which receives a power signal (from the electrical supply line, for example) at its input and supplies a direct current at its output via a power output 106. This current can be fixed or can vary over time. For example, the control circuit 102 can set the current required by the LED module 20 by using the reference channel IRef of the power circuit 104.
For example, the LED module 20 can also comprise an identification element which identifies the current required by the lighting module 20 (or control parameters in general). In this case, the control circuit 102 communicates with the identification element and adapts the operation of the electronic converter to the operating conditions required by the LED module.
FIG. 1 also shows two further switches 108 and 110.
The first switch 108 can be used to regulate the brightness of the module 20, in other words the light intensity emitted by the lighting module 20. For example, the switch 108 can be driven by pulse-width modulation (PWM) so as to short-circuit the LED module 20 selectively by diverting the current supplied by the generator 104 through the switch 108. As a general rule, however, the light intensity emitted by the LED module 20 can be regulated by regulating the mean current flowing through the lighting module, for example by setting a lower reference current IRef. The second switch 110 can be used to disable the power supply to the module 20. For example, an electronic converter 10 can disable the power supply when an error condition is detected, or for reasons of reliability, for example when a condition of excess current, excess voltage or excess temperature is detected.
FIG. 2 shows an example of a “simple” lighting module which comprises, for example, a chain of LEDs (or “LED chain”), in other words a plurality of LEDs connected in series. For example, FIG. 2 shows four LEDs, L1, L2, L3 and L4.
In this case also, switches can be provided for various purposes (for protecting and/or dimming the module 20, for example). For example, the switch SW5 connected in series with the LEDs L1-L4 can be used to disable the power supply to the module 20, and each of the switches SW1, SW2, SW3, SW4, connected in parallel, respectively, with one of the LEDs L1, L2, L3, L4, can be used to disable a single LED.
The function of the switch 108 of the converter 10 could therefore also be provided by means of a switch in the module 20 which selectively short-circuits the light sources L of the module 20.
As a general rule, a switch of this kind is sufficient if the module 20 is supplied with a regulated current. However, if the module 20 is supplied with a regulated voltage, a current regulator must be connected in series with the light sources in order to limit the current. In this case, the dimming function could also be provided by means of this current regulator, for example:
a) by selectively activating or disabling the current regulator by means of a drive signal such as a PWM signal, or
b) if a regulatable current regulator is used, by setting the reference current of this current regulator.
There are also “intelligent” lighting modules which comprise a control unit, and typically a digital communication interface. These lighting modules are typically capable of controlling control parameters of the lighting module and/or the dimming function.
As a general rule, a lighting system therefore comprises numerous sub-circuits which control the operation of the electronic converter 10 and/or the module 20.
Consequently, there are problems of compatibility between electronic converters and lighting modules, if these are not of the same type. This is because an electronic converter intended for use with a simple lighting module cannot recognize an intelligent lighting module, and vice versa. Consequently, the correct lighting module must be selected for a specific electronic converter, or vice versa, and when an electronic converter is replaced by a converter of a different type all the lighting modules must also be replaced.
However, it is inconvenient to use only one type of lighting module. For example, the simpler lighting modules are unable to offer some control parameters. A possible solution to this problem could be to use a control unit in the simpler modules as well. However, such a control circuit would be rather costly and would therefore make this solution inefficient.
Patent application WO 2009/081424, the content of which is incorporated herein by reference, describes, in this context, an electronic converter capable of providing a dimming function for simple 20a and intelligent 20b lighting modules.
In particular, as also shown in FIG. 3, the electronic converter 10 is configured for supplying the lighting modules with a regulated voltage, for example 24 V d.c., applied between a power supply line Vcc and a ground GND. In this case, the simple lighting modules 20a each comprise a light source L connected in series with a current regulator 120, and the light intensity is set directly by means of a PWM signal. The intelligent lighting modules 20b each comprise a light source L and a digital communication interface for receiving a data signal DATA, such as a serial communication receiver SR. In this case, the circuit SR detects the digital communication signal, analyses the signal and retrieves the data DATA. On the basis of the transmitted data, the circuit SR sets the light intensity of the light source L by using a corresponding regulatable current regulator.
In particular, this document teaches that the PWM signal and the data signal DATA can be transmitted on the same line 122 by connecting this line selectively to the ground GND by means of an electronic switch 16, such as a power transistor. In general, this document teaches that the PWM signal can be controlled as a function of a dimming signal DS, and the digital communication signal DATA can be used to transmit any data DF, additionally comprising the data for regulating the brightness of the intelligent lighting modules 20b. 
However, although this document partially resolves the problem of compatibility between different lighting modules, this solution does not allow an intelligent lighting module to be used with an electronic converter intended exclusively for use with a simple lighting module.